1. Field of the Invention
This invention relates to mud pumps, and more specifically to detecting internal defect conditions of a mud pump and monitoring performance of the mud pump.
2. Description of the Related Art
In a drilling operation, whether offshore or on land, teeth of a drill bit grind the rock and break it into small pieces. These rock pieces must be continuously removed from the path of the drill bit for the operation to continue. To that end, a mud pump injects drilling fluid or mud fluid in the form of a jet to remove the cut rock pieces from the path of the drill bit so that the operation may continue. Thus, the mud pump plays the role of heart in keeping the mud fluid flowing to remove the broken rocks and facilitate movement of the drill bit. In modern drilling operations, without the operational mud pump(s), the drilling comes to a halt.
A mud pump is a large heavy-duty, high-pressure reciprocating pump. A typical pump is a single- or double acting, two or three-cylinder piston pump whose pistons travel in replaceable liners and are driven by a crankshaft actuated by an engine or a motor. The pump is typically positioned on the drilling platform.
The lubricating fluid also called mud is continuously used for drilling operations. The mud is usually placed in steel tanks on a rig, where the mud is circulated through the wellbore during drilling and well workover operations. In addition to its function of bringing cuttings to the surface, drilling mud cools and lubricates the bit and drill stem, protects against blowouts by holding back subsurface pressures, and deposits a mud cake on the wall of the borehole to prevent loss of drilling fluids to the formation.
The pump forces the drilling mud through the drill pipe and drill collars and to the drill bit. The drilling mud jets out from the bit nozzles with great speed and moves the debris out of the path of the drill bit. The contaminated mud then moves back up to the surface for filtering and further processing for reuse. Since the pump interior parts come in contact with the mud including rock pieces of varying sizes, and experience harsh environment including an extensive vibratory environment, damage may occur to those parts. In general, the pump components, like liners, valves, seats, etc., degrade gradually and it is difficult to determine when the pump may be suffer functional failure.
These mud pumps are expensive pieces of machinery and are integral to a drilling operation. When the mud pump breaks, drilling operations must stop, and either the drilling contractor or operator has to bear the expenses for the associated downtime. At current prices, these costs may run from $2,000 to $20,000 per hour. Down times of a few days can be very expensive. Many groups have experimented with mud pump monitors, but have tried to solve the problem by mounting detection and monitoring sensors inside the pump itself. These attempts have failed for two main reasons. Firstly, the sensors are exposed to a hostile environment like high pressures (up to 7500 PSI), excessive heat, and corrosive fluids where the sensors are easily damaged and become useless. Secondly, machine tolerances are so small in high-pressure pumps, like mud pumps, that attaching an additional piece (in the form of a replaceable sensor) is not only impractical but also adversely affects pump performance.